Good on ya, they are pretty sweet shotguns, ideal for the dove field.
Take the forearm off by loosening the knurled screw at the end. Once off turn the barrel 90 degrees and pull forward. The trigger group comes out by removing the pins. The bolt/carrier assembly will easily come out.
I'm working from memory- haven't disassembled mine in quite awhile. If you get hung up, PM me.
Clean your barrel, and inspect the bore well. It is a slim steel bore with fibreglass wraps on the outside. The bores seem prone to pitting. If it is significant, there is a risk of a blowout.
Barrels are out there, but few and far between. You could expect to pay 80-150.00 for a new one. If what you have is a fixed choke, you may consider another barrel choked differently.
